I have the same problem. In all of my DAWs (FLStudio, Reason, LMMS), whenever the plugin is tried to be loaded i get the "serial not found" error message. On my other PC (both Windows 10 btw) it works without problems. Can't find the registration tool you guys talking about but i registered the plug in, at least thats what it says in my Synapse Account Area. Tried to reinstall it, which doesn't help. I'm using Windows 10 64 bit.